1. Field of the Invention
The present invention relates to an image forming apparatus in which a desired image is formed onto a recording medium such as a recording paper by using a flash light, and a color toner used therein. In particular, the present invention relates to an image forming apparatus in which, by employing a toner having a predetermined relationship with the flash light, a clear color image which has a high fixing quality can be formed by effectively utilizing the optical energy, and the above-mentioned toner.
2. Description of the Related Art
In a generally used electrophotographic image forming apparatus, a desired printed image is obtained through the following processes: (1) charging of a photosensitive body; (2) exposure of the photosensitive body (forming a latent image thereon); (3) development of the latent image with a toner; (4) transfer of the toner image onto a medium; and (5) fixing the toner image onto the medium.
The above-mentioned fixing of the toner image onto the recording paper or the like is achieved by a method of performing one of or both pressurizing and heating so as to melt the toner and then solidify and fixing it; or a method of irradiating optical energy so as to melt the toner and then solidify and fixing it.
Recently, the method of using optical energy has attracted attention as this method eliminates any problem occurring due to pressurizing or heating. That is, as this optical fixing method does not need pressuring toner for fixing it, it is not necessity to cause the toner to come into contact with (be pressed onto) a fixing roller or the like. Accordingly, no problem in that image resolution (reproducibility) is degraded through fixing process occurs.
Further, in this method, there is no need of heating by using a heat source, no waiting time for performing an actual printing operation until the heat source (such as a fixing roller) reaches a predetermined temperature through preheating is needed. Thus, it is possible to perform printing immediately after power is turned on.
Furthermore, as no high temperature heat source is needed, it is possible to prevent the temperature within the apparatus from increasing much. Further, there is no problem such that recording paper ignites by heat of the heat source when recording paper jams in the fixing device due to systematic failure.
However, in the optical fixing method, a fixing quality of a color toner of blue or red having a low light absorption rate is low in comparison to a case of a black toner. In order to solve this problem, many proposals have been made for improving the fixing quality by adding infrared ray absorbent into the toner.
For example, Japanese Laid-Open Patent Applications Nos. 58-102247, 58-102248, 60-63545, 60-63546, 60-57858, 60-57857, 60-131545, 60-133460, 61-132959, 6-348056, 7-191492, 10-39535, 11-38666, 11-125930, 11-125928, 11-125929, 11-65167, and, further, International Patent Publication WO99-13382, Japanese Laid-Open Patent Applications Nos. 2000-35689, 2000-147824, 2000-155439 disclose adding a material which absorbs light in the infrared zone so as to attempt both clear color and satisfactory optical fixing quality. However, it has not been possible to achieve a satisfactory fixing quality.
With regard to fixing of toner, Japanese Laid-Open Patent Application No. 63-231361 discloses a technique of causing light of wavelength of 4000 through 6000 nm to be absorbed by a binder resin for toner. However, there is a limit for improving the fixing quality of a color image by increasing a light absorption rate through modification of a resin.
The present invention has been devised in order to solve the above-mentioned problems, and, to provide a color image forming apparatus in which fixing is performed by using a toner including an infrared ray absorbent having an effective absorption for a light emission peak of a fixing light source, and the toner. By configuring so, it is possible to perform fixing of the color toner in an improved level corresponding to that of a monochrome toner.
A color image forming apparatus according to the present invention forms a color image on a recording medium by using a toner at least comprising binding resin, coloring agent and infrared ray absorbent (which may comprise one or a plurality of types of infrared ray absorbents), and a light source for causing the toner to melt,
wherein:
the light source has at least one light emission peak in a range of 500 nm through 3000 nm; and
setting is made such that the following relationship is satisfied:
xe2x80x83|xcexxe2x88x92xcex9| less than 100 nm
where:
xcex denotes the wavelength of the light emission peak; and
xcex9 denotes the wavelength of an absorption peak wavelength of the infrared ray absorbent.
A color image forming apparatus according to another aspect of the present invention forms a color image on a recording medium by using a toner comprising at least binding resin, coloring agent and infrared ray absorbent (which may comprise one or a plurality of types of infrared ray absorbents), and a light source for causing the toner to melt,
wherein:
the light source has a plurality of light emission peaks having wavelengths of xcex1, xcex2, xcex3, . . . , xcexn in a range of 500 nm through 3000 nm; and
setting is made such that the following relationship is satisfied:
|xcex1xe2x88x92xcex91| less than 100 nm, and, also, |xcex2xe2x88x92xcex92| less than 100 nm
where xcex91 and xcex92 denote the wavelengths of absorption peak wavelengths of the infrared ray absorbent.
In each of the above-mentioned configurations, by employing the toner which includes the infrared ray absorbent which efficiently absorbs the optical energy at the light emissions peaks of the light source, it is possible to form a color image having superior fixing quality and hue. Further, in comparison to the related art, it is possible to reduce the required amount of infrared ray absorbent to be used, and, thus, to reduce the cost.
Further, assuming that the above-mentioned light emission peaks xcex1, xcex2, xcex3, . . . , xcexn have light emission intensities in the stated order from the highest one, the absorption peak wavelengths xcex91 through xcex9n of the infrared ray absorbent may be set corresponding to the wavelengths xcex1 through xcexn.
Thereby, as the toner includes the infrared ray absorbent which utilizes the energy at the light emission peaks having the high light emission intensities, it is possible to utilize the optical energy more efficiently in forming a color image.
The light source may comprise a flash lamp having the light emission peaks in a range of 800 through 850 nm and also in a range of 850 through 1000 nm; and
the infrared ray absorbent may have the absorption peak in at least one of a range of 700 through 900 nm and a range of 900 through 1100 nm.
Further,
the (first) infrared ray absorbent having the absorption peak in the range of 700 through 900 may comprise at least one of cyanine, anthraquinone, phthalocyanine, naphthalocyanine, polymethine, and nickel complex; and
the (second) infrared ray absorbent having the absorption peak in the range of 900 through 1100 nm may comprise at least one of aminium, diimonium, stannic oxide, ytterbium oxide, ytterbium phosphate, and nickel complex.
Thereby, through the effective combination between the flash lamp and infrared ray absorbent, it is possible to perform effective color image formation.
An addition amount of the infrared ray absorbent to the toner may be 0.01 through 12 weight parts with respect to 100 weight parts of toner.
The energy of the light source may be 1.0 through 6.0 J/cm2.
Further, a color toner according to the present invention is melted by optical energy from a light source having a plurality of light emission peaks having wavelengths of xcex1, xcex2, xcex3, . . . , xcexn in a range of 500 nm through 3000 nm, and comprises at least binding resin, coloring agent and infrared ray absorbent,
wherein at least the following relationship is satisfied:
|xcex1xe2x88x92xcex91| less than 100 nm, and, also, |xcex2xe2x88x92xcex92| less than 100 nm
where xcex91 and xcex92 denote absorption peak wavelengths of the infrared ray absorbent.
Then, assuming that the above-mentioned light emission peaks xcex1, xcex2, xcex3, . . . , xcexn have light emission intensities in the stated order from the highest one, the absorption peak wavelengths xcex91 through xcex9n of the infrared ray absorbent may correspond to the wavelengths xcex1 through xcexn.
Other objects and further features of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.